1. Field of the Invention
This invention relates to well tools and more particularly to devices for releasably stopping movement of well tools at known locations in well flow conductors.
2. Description of the Prior Art
In performing operations in wells through use of well tools run thereinto on tool strings utilizing wireline or pumpdown equipment and techniques, it is often desirable to know the location of such tools in the well. When using wireline tools, the wireline passes through a meter which indicates the general location of the tools at all times with respect to a zero-point usually at the earth's surface. Such metering of the wireline is satisfactory for most downhole operations but oftentimes not accurate enough. Inaccuracies in measuring wireline arise because of factors such as: a worn metering wheel, the metering wheel not designed for the wireline in use, the tension on the wireline as it is lowered into the well is not the same as when it is withdrawn, or slipping of the meter wheel relative to the wireline, or malfunction of the metering device.
In pumpdown operations, the string of tools, also called a tool train, includes piston units, thus adapting the tool train for being moved into and out of the well by fluid pressure as fluids, such as oil or water, or the like, are circulated through the well. It is highly desirable to know the location of the tool train in the well, and in the past such knowledge was for the most part obtained from measuring the volume of liquids pumped into the well. The measurements thus obtained were only approximate, and the true location of the tools was often questionable. Errors occurred because of several factors. For one thing, some fluid bypasses the tool train. Pumpdown piston units have a built-in bypass passage. Also, some fluid passes around the pistons as they pass by enlarged bores, as in pipe couplings, valves, landing nipples, etc. Further, the flow meter may not measure the pumped liquid accurately. Then too, the volume of the flow conduit through which the tool train is moving may not be known precisely.
Because of the errors mentioned above which causes some guesswork in attempts to determine the location of a tool string in a well, means other than measuring wireline or pumped fluids must be used, for instance, reference points (checkpoints) fixed in the well flow conductor.
The following prior art patents are believed pertinent to this invention.
3,696,868, 3,827,490, 3,937,279
U.S. Pat. No. 3,937,279 issued to George M. Raulins on Feb. 10, 1976 and was assigned to Otis Engineering Corporation, Dallas, Tex., employer of the inventors of the instant invention. Pat. No. 3,937,279 illustrates and describes a device for use as a part of a well flow conduit. It comprises a sliding sleeve having collet fingers with bosses thereon and slidably disposed in a housing having a cam shoulder therein. In one position of the sleeve, the device does not restrict the bore of the flow conductor, but when the sleeve is shifted to its other position, the collet fingers are cammed inwardly and held in a position wherein their bosses definitely restrict the bore such that the device will stop well tools of ordinary size and may even catch tools of ordinary size should they be dropped inadvertently from above. Thus, this device provides a "no-go" shoulder in the well when the sleeve is in one position but is nonrestricting when the sleeve is in the other position. To shift the device between its restricting and nonrestricting positions, a shifting tool must be run into the well on a string of tools to engage and shift the sleeve. A special trip of the tools must be made for each shifting of the sleeve. When a string of tools has been stopped by the device of Pat. No. 3,937,279, the device cannot at that time be shifted to nonrestricting position to let the tool string move therepast since shifting of the sleeve requires a separate trip into the well with a shifting tool as explained earlier.
U.S. Pat. No. 3,696,868 issued to Donald F. Taylor, Jr. on Oct. 10, 1972 and shows that it is old to operate a downhole well tool remotely from the surface by pressurized control fluid, the control fluid being supplied from a surface control unit and being conducted to the well tool downhole via a fluid conduit and admitted into the well tool through a lateral port to act upon the pressure responsive area of a longitudinally slidable annular piston.
U.S. Pat. No. 3,827,490 issued to Howard H. Moore, Jr., et al. on Aug. 6, 1974 and teaches use of side Pocket mandrels having an orienting sleeve therein, this orienting sleeve having an orienting slot and a guide surface below the slot and directed upwardly and inwardly towards the bottom of the slot, and a shoulder positioned at the top of and blocking the slot. This shoulder is for stopping a kickover tool but is fixed and is not retractable.
The present invention overcomes such difficulty by providing tool stopping devices which are remotely actuated from the earth's surface by fluid pressure and can be shifted at will. Well systems in which a plurality of such devices installed at known locations or checkpoints are used in a well having one or a plurality of well flow conduits, including well tubing, and even flow lines, are provided, and such devices may be actuated simultaneously or otherwise to stop well tools at such known locations and then let them move therepast to be stopped at the next location so that the exact location of the tool string can be known at least when they reach these successive checkpoints. Thus, the invention also provides methods of determining the arrival of well tools at known checkpoints in wells, thus indicating their true location.
Thus, the present invention is an improvement over the invention of George M. Raulins which is disclosed in U.S. Pat. No. 3,937,279 discussed hereinabove.